High molecular weight epoxy resins have been previously prepared by reacting phenolic compounds with epoxide compounds in the presence of such catalysts as inorganic bases, amines, ammonium salts, phosphine and phosphonium salts such as described in U.S. Pat. Nos. 3,284,212; 3,547,881; 3,477,990; 3,948,855 and 4,438,254. However, most of these catalysts while being suitable for catalyzing the reaction between phenolic hydroxyl-containing compounds and epoxides, most of these catalysts possess some undesirable feature such as poor reactivity which requires high catalyst levels and long reaction times; poor selectivity to the reaction of phenolic hydroxyl groups with epoxides, difficulty in deactivation and the like.
In batch processes or in a continuous process for the production of advanced resins such as by the extruder process disclosed in U.S. Pat. No. 4,612,156 it would be highly desirable to have available for use in that process a catalyst which would be highly active, highly selective to the reactive hydrogen atoms, particularly phenolic hydroxyl groups, and easily deactivated.
It would also be desirable to have a catalyst which will result in fast cures when an epoxy resin was cured with a curing agent, particularly with acid anhydrides.